Mark Pine

Neuroscientists have demonstrated that the focusing of attention in consciousness is associated with specific frequencies of neuronal activity in the brain, and anticipation of an event requiring attention is associated with other specific frequencies.

The researchers, at the University of Chicago, Baylor College of Medicine, and Rush University, showed that one person’s conscious attention to instructions displayed on a computer screen was signaled by the onset of beta oscillations (12-30 Hz) of local field potentials in his motor cortex. They also demonstrated that delta oscillations (0.5-1.5 Hz) in the same region indicated the subject’s enhanced readiness to focus attention on an anticipated instruction.

The research was reported last Thursday in the journal Neuron. An article on the findings appeared in ScienceDaily the next day.

The subject of the experiment was a quadriplegic person, whose brain had been implanted with a computer chip holding an array of 100 electrodes. The device allows paralyzed individuals to control the motion of a computer cursor with their brain. However, the chip also permits recording of local field potentials similar to brain waves on an EEG.

In the experiment the subject watched a rhythmic sequence of five instructions to move the cursor, as they appeared on the computer screen. But the person was told to carry out only the second and fourth instructions. The recording from the electrode showed that the amplitude of beta frequency brain waves increased as the subject waited for the relevant instructions to appear, and the beta amplitude peaked just before they did. The beta amplitude subsided between the relevant instructions, when the subject was ignoring the other instructions not performed.

The electrode recordings also showed that the amplitude of delta frequency waves entrained to a periodicity that followed to the timing of the appearance of the instructions. The scientists inferred that the delta waves play a role in enhancing a readiness to pay attention, so that maximum beta activity would coincide with the appearance of the anticipated input.

The relationship of the two frequencies is like the melody and bass of a tune, one scientist explained. “The slow rhythm is kind of like the rhythm section, and you anticipate notes at particular moments in time based on that slower rhythm,” he said.

The researchers hope that the ability to track a person’s attention could help people to improve their concentration. In the case of paralyzed people connecting with computers, attention monitoring might help to improve their control of the computer.

The discovery also clarifies an important issue regarding the nature consciousness. Brain scientists sometimes fail to distinguish between consciousness, an inclusive concept, and attention, a specific function of consciousness. For example, we sometimes say that we become conscious of a particular feeling or thought. We don’t mean that we are not already conscious, but rather a feeling or thought comes to our attention—we notice it.

An article touching on this issue appeared last December in Scientific American. Daniel Bor, a neuroscientist and author of the report, wrote in a comment: “Some researchers suggest that attention and consciousness are one and the same, in fact. A very interesting question.”

The new research points to the answer by demonstrating that particular brain waves in the beta frequencies are associated with the function of attention. Yet the contemporaneous occurrence of delta waves also shows that consciousness is present, whether or not the function of attention is engaged. (Of course, the fact that the subject was alert and responsive (conscious) during beta amplitude troughs also shows that consciousness is distinct from attention.)

This difference was graphically illustrated in the first episode of the Charlie Rose’s remarkable series of programs on brain research. One of the brain scientists, Tony Movshon, used the Necker cube to demostrate that the brain can synthesize two alternative perceptions of one diagram of a cube. In experiencing this familiar but striking optical illusion, we discover that as we shift our function of attention, we see one version of the cube, then the other. But our function of consciousness remains with us all the time, and the two perceptions occur within our one consciousness.